Process of making alkali perborates.



0 LIEBKNECHT.

PROCESS OF MAKING ALKALI PERBORATES.

APPLICATION FILED FEB. 29. 1916.

1,281,983. Patented 001;. 15, 1918.

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351; 11 4 Qttoznmp \A,Lu. 5 ML tum OTTO LIEBKNECHT,FRANKFORT-ON-THE-MAIN, GERMANY, ASSIGNOR TO THE BOESSLER & HASSLAGHERCHEMICAL 00., OF NEW OF NEW YORK.

YORK, N. Y., A CORPORATION rnocnss or MAKING nLxnLI rnmaonarns.

To all whom it may concern:

Be it known that I, O'rro LIEBKNECHT, a citizen of Germany, residing atFrankforton-the-Main, Germany, have invented certain newand usefulImprovements in Processes of Making Alkali Perborates; and I do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same, reference being had to theaccompanying drawings, which form a part of this specification.

This invention relates to processes of makin alkali perborates and itrelates particular y to the electrolytic production of alkali perboratesin the presence of certain electrodes possessing properties favorablefor such electrolysis.

In the electrolytic production of alkali perborates, such as sodiumperborate, from solutions of alkali borates and alkali carbonates asdescribed in my applications filed January 6, 1916, under Serial Nos.70,591 and 70,592, the material of which the anode is made isnecessarily such as will not be attacked by oxygen. As to the cathodethere arises the presumption that any material acting as a catalyzer tothe sodium perborate should be excluded and that the metals not exertingthis harmful function, as for instance zinc, tin, or aluminium, would beprimarily suitable in the construction of such a cathode.

' I have been astonished, however, to find that said metals, mentionedabove, are unsuitable; aluminium for instance is strongly affected, bythe discharge of the alkali metal at the cathode, whereas tin is more orless covered with a thick layer of a brown powder, which is probably afinely divided metal mixed with the generated sodium perborate. Zincdisplays a behaviorsimilar to that of tin; none of these metals cantherefore be considered for making a cathode for the production ofalkali perborates.

Though this electrolytic process is extremely sensitive towardcatalyzers, I have now made the surprising observation that the cathodemay be made with great suc- Speclflcation of Letters Patent.

Application filed February 29, 1916. Serial No. 81,119.

Patented Oct. 15, 1918.

cess of such conductors which themselves or the compoundsof which, actas catalyzers, as for instance lead, iron, nickel, copper, silver orcarbon.

The cathodes made from these latter materials do not change at all andgive satisfactory yields; in the finished alkali perborate thesematerials cannot be found to be present.

I have found through experiments, that in working the process accordingto my invention, it is advantageous to use cathodes made of materialswhich are characterized by their hydrogen potential equaling zero, or avalue which differs but slightly from zero. Or to express it with otherwords, it is advantageous to apply cathodes made of materials whichdisplay no cathodic excess potential, or but a shght cathodicexcesspotential. Such materials, for instance, are iron, silver, nickel,copper.

Figure 1 of the drawings is a fragmentary sectional View showing oneform of apparatus designed for use in connection with my invention andFig. 2 is a similar view showing a modification.

Similar numerals of reference indicate similar parts throughout theseveral views.

1 indicates the wall of the electrolytic vessel. *2 the electrolyte. 3the electrode and 4 the conductor. 5 indicates a protective coating onconductor 4: and 6 and 7 indicate suitable packing rings for holding theconductor in the wall of the electrolytic vessel in the form shown inFig. 1.

Though I have found that generally no further precautions have to beobserved in the application of cathodes made from these materials, Ihave found it suitable to protect the conducting rods of the cathodes,as far as they protrude from the electrolyte, against the action of theelectrolyte and air which latter is noticeable on the surface of theformer. the cathode in such a manner as to prevent the same from gettinginto contact with air; for instance, by providing for the cathode aconductor which enters the bath laterally, that is, below the surface ofthe electrolyte. Thereby, not only the cathode but the con- To this endI am disposing till ducting rod also is precluded from coming intocontact with the air. An illustration of this novel feature is given inFig. lof the drawings. This very efiect may be attained in a modifiedmanner by coating the conducting rods of the cathode, at those portionsWith "which the rods enter the electrolyte, with a non-porous andnon-corrosive material capable of resisting the efiect of the combin daction of the electrolyte and air.

Such a protective coating may be made by placing a layer of metal,resistant to the corrosive action, as for instance platinum, on theportions to be protected, or a coat of resistant pain may be applied,or, it the "form of the cathode permits it, a rubber tubing may heslipped over the portion to be protected. An illustration of this lattermodification is reproduced in Fig. 2 of the drawings.

Through eXperimentsT have further discovered the surprising fact thatamong all the materials suitable for making cathodes, nickel occupies anexceptional position in as far as nickel is not liable to corrosion evenWithin thev contacting zone or" the electrolyte and air. Tn consequenceof this discovery, cathodes made or any materials otherwise than nickel,may be protected Within the danger zone by means of nickel. Thus,electrodes made of iron and Which in practical Working on amanufacturing scale, have proved especially satisfactory may be providedWith a nickel coating, or may consist of nickel in the threatenedplaces. The applicability of nickel for these purposes could not beanticipated, all the less, as the rest or" the base metals suitable forthe purpose under consideration, are all liable to be at- :tected by thecombined action of the elem trolyte and air.

What l claim as my invention is:

1. The process of making alkali perborates, consisting in electrolyzinga solution of alkali borate and alkali carbonate in the presence of acathode made of conductive material acting per so as a catalyzer to analkali perborate.

2. The process of making alkali perborates, consisting in electrolyzinga solution of alkali borate and alkali carbonate in the presence otacathode made or" conductive material, the compounds of which act as acatalyzer to an alkali perborate.

3. The process of making alkali perborates, consisting in electrolyzinga solution of alkali borate and alkali carbonate in the presence of acathode made of conductive material acting per 86 as a catalyzer to analkali perborate and protecting the exposed parts of the cathode againstthe combined action of the electrolyte and air by covering said partsWith a coat of mat..-

rial resistant to the corrosive action of the electrolyte and air.

l. The process of making alkali perborates, consisting in electrolyzingasolution of alkali borate and alkali carbonate in the presence of acathode made of conductive material acting per so as a catalyzer to analkali perborate, and displaying substantially no cathodic excesstension.

5. The process of making alkali perborates, consisting in electrolyzinga solution of alkali borate and alkali carbonate in the presence of acathode made of conductive material displaying substantially no cathodicexcess potential and the compounds of which material act as a catalyzerto an alkali perborate.

6. The process of making alkali perborates, consisting in electrolyzinga solution of alkali borate and alkali carbonate in the presence of acathode made 01 conductive material acting per so as a catalyzer to analkali perborate and displaying but an inconsiderable excess potential.

7. The process of making alkali perborates, consisting in electrolyzinga solution of alkali borate and alkali carbonate in the presence of acathode containing iron.

8. The process or making sodium perborate, consisting in electrolyzing asolution of a sodium borate and sodium carbonate in the presence of acathode made of conductive material acting per so as a catalyzer for analkali perborate.

9. The process of making sodium perborates, consisting in electrolyzinga solution of a sodium borate and sodium carbonate in the presence of acathode made of conductive material, the compounds 01 which act as acatalyzer to an alkali perborate.

10. The process of making sodium perborates, consisting in electrolyzinga solution of a sodium borate and sodium carbonate in the presence of acathode made of conductive material acting per so as a catalyzer to analkali perborate and protecting the exposed parts of the cathode againstthe combined action of the electrolyte and air by covering said partswith a coat of material resistant to the corrosive action of theelectrolyte and air.

ll. The process of making sodium perborates, consisting in electrolyzinga solution of a sodium borate and sodium carbonate in the presence of acathode containing iron.

12. The process of making sodium perborates, conslsting in electrolyzinga solution v of a sodium borate and sodium carbonate in the presence ofa cathode made of conductive material acting per 86 as a catalyzer foran alkali perborate and displaying substantially no cathodic excesspotential.

13. The process of making sodium perborates, consisting in electrolyzinga solution of a sodium borate and sodium carbonate in In testimonywhereof I have signed this tlve material displaying but aninconsiderlng'witnesses.

able excess of cathodic potential and acting OTTO LIEBKNECHT. 5 per 86as a catalyzer to an alkali perborate Witnesses:

and being protected against contact with JEAN GRUND,

a1r. CARL GRUND.

the presence of a cathode made of conducspecification in the presence oftwo subscrib-

